Earth microbes on the moon

Earth microbes on the moon

Three decades after Apollo 12, a
remarkable colony of lunar survivors revisited

September
1, 1998: For a human, unprotected space travel is a short
trip measured in seconds.

What could be worse for would-be space travelers than a catastrophic
breach in their protective spacesuits, the high-tech, multilayered
fabric blanket that balloons under the pressure of a life-saving
flow of oxygen and insulates against the frozen harshness of
deep-space vacuum?

But for some kinds of microbes, the harshness of space travel
is not unlike their everyday stressful existence, the successful
execution of ingenious survival tricks learned over billions
of years of Earth-bound evolution.

Forthcoming anniversary

Space historians will recall that the journey to the stars
has more than one life form on its passenger list: the names
of a dozen Apollo astronauts who walked on the moon and one inadvertent
stowaway, a common bacteria, Streptococcus mitis, the
only known survivor of unprotected space travel. As Marshall
astronomers and biologists met recently to discuss biological
limits to life on Earth, the question of how an Earth bacteria
could survive in a vacuum without nutrients, water and radiation
protection was less speculative than might first be imagined.
A little more than a month before the forthcoming millennium
celebration, NASA will mark without fanfare the thirty year
anniversary of documenting a microbe's first successful journey
from Earth.

Apollo 12
remembered

In 1991, as Apollo 12 Commander Pete Conrad reviewed the transcripts
of his conversations relayed from the moon back to Earth, the
significance of the only known microbial survivor of harsh interplanetary
travel struck him as profound:

"I always thought the most significant thing that we
ever found on the whole...Moon was that little bacteria
who came back and lived and nobody ever said [anything] about
it."

Although the space-faring microbe was described in a 1970
Newsweek article, along with features in Sky and Telescope
and Aviation Week and Space Technology, the significance
of a living organism surviving for nearly three years in the
harsh lunar environment may only now be placed in perspective,
after three decades of the biological revolution in understanding
life and its favored conditions.

As the lunar voyagers answered a similar question more than
a century ago, in Jules Verne's classic, From the Earth to
the Moon: "To those who maintain that the planets are
not inhabited one may reply: You might be perfectly in the
right, if you could only show that the earth is the best possible
world."

Three decades, the biological revolution

To a biologist, freeze-drying microbes for harsh space travel
conjures up rather mundane kitchen science, a simple reenactment
of how a yeast packet taken from the freezer can make bread dough
rise prior to baking. But to a new breed of biologist exploring
the harshest conditions on Earth, how a delicate microbe manages
to counteract vacuum, boiling temperatures, burning radiation,
and crushing pressures deep in the frozen icecaps is the study
of life itself.

For example, only now after
30 years of biological progress can scientists begin to scan
down the genetic script underlying the causes of malaria, syphilis,
cholera and tuberculosis. Within a few years, it is estimated
that 50 to 100 complete genomes of living organisms will be entirely
deciphered, presenting the first opportunities for deep evolutionary
comparisons and insights into exactly the remarkable means by
which the common Strep. bacteria could revive itself after
2.6 years on the moon.

The Surveyor probes were the first U.S. spacecraft to land
safely on the Moon. In November, 1969, the Surveyor 3 spacecraft's
microorganisms were recovered from inside its camera that was
brought back to Earth under sterile conditions by the Apollo
12 crew.

The 50-100 organisms survived launch, space vacuum, 3 years
of radiation exposure, deep-freeze at an average temperature
of only 20 degrees above absolute zero, and no nutrient, water
or energy source. (The United States landed 5 Surveyors on the
Moon; Surveyor 3 was the only one of the Surveyors visited by
any of the six Apollo landings. No other life forms were found
in soil samples retrieved by the Apollo missions or by two Soviet
unmanned sampling missions, although amino acids - not necessarily
of biological origin - were found in soil retrieved by the Apollo
astronauts.)

How this remarkable feat was accomplished only by Strep.
bacteria remains speculative, but it does recall that even our
present Earth does not always look as environmentally friendly
as it might have 4 billion years ago when bacteria first appeared
on this planet.

Recent biological progress

May 1995: Deciphering
of the first complete gene of a living organism (1,749 genes
of the Hemophilus influenzae bacteria). In the New
York Times, Nobel Laureate and co-discoverer of the DNA double
helix, James Watson said: "I think it's a great moment in
science."

September 1995:
Deciphering of the smallest known viable genome on the planet,
Mycoplasma genitalium, giving the first genetic script
of what separates life from non-life

July 1996: Deciphering
of the first genome from the third "super kingdom"
of life, the Archea, and the organism Methanococcus
jannaschii, a deep-sea hot vent microbe, separating bacteria
and eukaryotes (such as plants and animals)

1997: Deciphering
the genome of the human pathogen, Helicobacter pylori,
the ulcer-causing bacteria that dwells in the stomachs of
half of the people on Earth

1998: Deciphering
the microbial genome, Deinococcus radiodurans, having
the remarkable capacity to withstand massive space-scale doses
of over 1.5 million rads of radiation--3,000 times the dose that
would kill a human in space

Culture plate from Surveyor 3 camera foam
sample (1 cc volume of polyurethane foam). Samples of the microorganism
(left) were sent to the US Communicable Disease Center
at Atlanta, Georgia, which confirmed it as Streptococcus mitis.
a common harmless bacteria from the nose, mouth and throat in
humans.

The Streptococcus genus consists of Gram-positive
bacteria which appear as chains under microscopic observation.
Members of Streptococcus can be aerobic, anaerobic, or microaerophilic.
The organisms in this genus are characterized by a coccus appearance,
a thick cell wall, and aerobic action on glucose. The Surveyor
foam sample was cultured in bacterial media (Thioglycollate)
at 37 C. The facultative streptococci are the largest group of
bacteria isolated from the oral cavity. They comprise almost
50% of the organisms isolated from plaque and the gingival sulcus.
This most abundant oral streptococci are the alpha-hemolytic
(Viridans) streptococci, which are part of the normal flora and
symbiotically limit the growth of competing harmful bacteria
in the mouth.

It has been calculated that the normal human
houses about a trillion bacteria on the skin, 10 billion in the
mouth, and 100 trillion in the gastrointestinal tract. The
latter number is far in excess of the number of eukaryotic cells
in all organs which comprise the human host. It is sometimes
said quite simply that there is more of "them" than
"you'' in you. The normal flora occupy available colonization
sites which makes it more difficult for other microorganisms
(nonindigenous species) to become established.

Left: Streptococcus
genus, bacterial cells

Extremophiles: Life on the Edge

The Earth looked remarkably different when bacteria first
colonized the oceans and land. Oxygen was scarce. To many early
plants, cyanobacteria and anaerobic bacteria, oxygen was a poison.
The thin ozone layer that currently shields intense solar radiation
was largely unformed. Bacteria, originating under global conditions
very different from our present day, can be thought to be space
travelers already: over time the generational records of microbes
have sampled swings in environment here on earth that rival the
differences between today's Earth and some of the more hospitable
planetary outposts. The growing list of space-hardiness conditions
include:

Vacuum conditions,
with bacteria taken down to near zero pressure and temperature,
provided suitable care is exercised in the experimental conditions.

Pressure, with
viable bacteria after exposure to pressures as high as 10 tonnes
per square centimeter (71 tons/sq-in). Colonies of anaerobic
bacteria have recently been recovered from depths of 7 km (4.2
mi) or more in the Earth's crust.

Heat. Archaebacteria
that can withstand extreme heat have been found thriving in deep-sea
hydrothermal vents and in oil reservoirs a mile underground

Radiation, including
viable bacteria recovered from the interior of an operating nuclear
reactor. In comparison to space, each square meter on Earth is
protected by about 10 tons of shielding atmosphere.

Long preservation,
including bacteria revived and cultured after some 25 million
years of encapsulation in the guts of a resin-trapped bee.

"I should venture to assert, that
if these worlds are habitable, they either are, have been, or will be inhabited."

Jules Verne, From the Earth
to the Moon, 1877.

Hitchhiking across the
solar system

The streptococcus bacteria on Surveyor 3 might not be the
only interplanetary microbial hitchhikers. In 1996, researchers
at NASA's Johnson Space Center announced that they had found
evidence of microfossils in a Mars meteorite recovered from a
field of blue ice in the Antarctic.

The presence of polycyclic aromatic hydrocarbon [PAH] molecules
in the Allan Hills meteorite was taken as one sign that objects
in the rock are microfossils. Critics claim that the PAHs are
contamination from the ice.

The recent discovery of a 13th meteorite, apparently from
Mars, might help is resolving the issue.

"The fact that it was found in the Sahara means that
it can't possibly be contaminated with PAHs from ice," said
Richard Hoover, an X-ray astronomer at NASA's Marshall Space
Flight Center.

Hoover is part of two investigations that will develop tools
and techniques to prepare and examine specimens that may have
life forms. He also is planning a trip to Antarctica to look
for samples of life thriving under extreme conditions.

"We don't know how long this 13th rock has been in the
Sahara," Hoover said, "but finding another SNC [Mars
meteorite] is a very exciting result."

While long associated with rocket propulsion, NASA's Marshall
Space Flight Center also is deeply involved in space science
research. Recently, this has expanded to include astrobiology,
the study of life outside the Earth. In addition to Hoover's
work, Dr. David Noever, author of this article, is developing
a "D'Arcy machine," a program to help computers recognize
life forms in electron microscope and other images.

Microgravity Research and Astrobiology

NASA's mission is divided into four enterprises: Earth Science,
Space Science, Aeronautics and Space Transportation Technology,
and Human Exploration and the Development of Space (HEDS). Marshall
Space Flight Center is the designated lead center for microgravity
research, under the Human Exploration and Development of Space
(HEDS) enterprise in the 1998 NASA Strategic Plan. This directive
answers two important scientific questions:

What is the fundamental role of gravity
and cosmic radiation in vital biological, physical, and chemical
systems in space, on other planetary bodies, and on Earth, and
how do we apply this fundamental knowledge to the establishment
of permanent human presence in space to improve life on Earth?

HEDS also plays an important role working
with the other Enterprises to pursue answers to other fundamental
questions, including: Does life exist elsewhere than on our planet?

Above is a crystallization experiment
of complex proteins and macromolecules performed aboard the Space
Shuttle